1. Field of the Invention
This invention relates to the field of electronics. More specifically, the invention is directed to a circuit for a high speed analog multiplexer for data acquisition systems.
1. Description of the Prior Art
Analog multiplexers generally allow one of many signals to pass. This function lets many channels share one analog-to-digital, A/D, converter in a time slice fashion. Since the analog to digital converter is often the most expensive part of a data acquisition system, the ability to share the converter can significantly reduce the system cost. Known analog multiplexers provide a low resistance path from input to output for the chosen channel and a high resistance path to all other channels. Existing systems generally use analog switches comprised of parallel pairs of complementary channel MOSFETs. The outputs of such systems are all tied together to provide a single output. The sum of all MOSFET drain and source capacitances from all the off channels however, is seen at the output. Such an approach creates settling times that are too long to take advantage of state of the art analog-to-digital converters. Hence, current analog multiplexers have become the limiting factor in economical data acquisition system advancement.
Thus, there exists a continuing need for a faster analog multiplexer not limited by MOSFET source/drain capacitive discharge settling times to more efficiently take advantage of fast state-of-the-art analog-to-digital converters.